[unreadable] Non-typeable Haemophilus influenzae (NTHi) is the most common bacterial cause of exacerbations of chronic obstructive pulmonary disease (COPD). These exacerbations are characterized by a brisk inflammatory response with the accumulation of polymorphonuclear leukocytes (PMN) in the lungs of patients with COPD. Essential to this inflammatory response is the expression and secretion of proinflammatory cytokines by host respiratory cells in response to NTHi. The mechanisms, by which NTHi stimulate a proinflammatory response by host respiratory cells and the progressive airway destruction in COPD, is unclear. Therefore, the overlying hypothesis of the proposed research is that secreted, nonlipooligosaccharide (LOS), NTHi proteins (i.e., modulins) stimulate the production of proinflammatory cytokines from human respiratory cells contributing to the endobronchial inflammation in COPD. The long-term goal of this project is to define the mechanisms by which specific secreted NTHi modulin(s) affect the recruitment and activation of effector cells in NTHi endobronchial infection. This goal will be met through identifying, purifying, and characterizing one such secreted modulin and its corresponding gene from model H. influenzae strain Rd and analyzing the modulin's role in respiratory inflammation in vitro. We will study the following Specific Aims to address the hypothesis. Specific Aim I will identify the secreted modulin from H. influenzae that stimulates a proinflammatory response in respiratory epithelial cells by 1) isolating the secreted modulin from H. influenzae strain Rd; 2) analyzing the secreted modulin gene from H. influenzae strain Rd; and 3) reconstituting the H. influenzae strain Rd modulin activity using the purified modulin. Specific Aim II will assess the distribution and expression of the secreted modulin gene from clinical isolates of NTHi. These studies will provide important insights into the mechanisms of the host inflammatory response in NTHi endobronchial infection of COPD and potentially identify novel therapeutic strategies to be employed in the treatment of this debilitating disease. [unreadable] [unreadable]